Apparatus for releasing clutch and brakes to prevent wheel skid

ABSTRACT

A vehicle having a conventional clutch pedal and brake pedal is provided with an antiskid brake system wherein a wheel rotation sensor provides a signal for the automatic release and reapplication of the brakes during a substantial wheel lock condition. Upon the initial reception of the signal, the clutch will automatically be released and will be maintained in the release position during any subsequent automatic release and reapplication of the brakes during a continuous single operation of the brake pedal.

United States Patent Okamoto 3,637,057 [451 Jan. 25, 1972 SKID [72]Inventor: Tosiaki Okamoto, Toyota-shi, Japan [73] Assignee: Aisin SeikiCompany Limited, Toyota-shi,

Japan [22] Filed: Oct. 21, 1969 [21] Appl. No.: 868,141

[30] Foreign Application Priority Data Oct. 22, 1968 Japan ..43/76574[52] U.S.Cl. ..192/l3 R, 192/91 R, 188/181 A,

303/21 [51] Int. Cl ..Fl6d 67/04 [58] Field ofSearch .192/13R,4A;188/181 A References Cited UNITED STATES PATENTS 1,996,282 4/1935 Drabinet a1. ..l92/13 X 1,999,284 4/1935 Colvin 192/13 X 2,016,308 10/1935Wyllie t ..192/13 X 3,401,986 9/1968 Walker et a1. ..188/l81 A X3,473,850 10/1969 Lawrie ..188/181A X Primary Examiner-Benjamin W. WycheAltorneySughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT A vehiclehaving a conventional clutch pedal and brake pedal is provided with anantiskid brake system wherein a wheel rotation sensor provides a signalfor the automatic release and reapplication of the brakes during asubstantial wheel lock condition. Upon the initial reception of thesignal, the clutch will automatically be released and will be maintainedin the release position during any subsequent automatic release andreapplication of the brakes during a continuous single operation of thebrake pedal.

6 Claims, 2 Drawing Figures PAIENIEn-mzsm $631057 SHEET 2 OF 2 FIG. 2

APPARATUS FOR RELEASING CLUTCH AND BRAKES TO PREVENT WHEEL SKID Thisinvention relates to a method for the prevention of lateral slippage ofa powered vehicle, frequent appearing in the course of sudden andconsiderable hydraulic brake applications.

As is commonly known, the rotational speeds of wheels of a poweredvehicle or the peripheral speeds of the heels may frequently becomeconsiderably and excessively slower than 10 the occasional advancingspeed of the vehicle in the course of hydraulic brake application. Insuch cases, so-called slips could certainly appear between the vehiclewheels and the ground surface.

It has been therefore already proposed for providing an efficientcounter measure to sense the excessively retarded peripheral speed ofvehicle wheels relative to the absolute running speed of the vehicleagainst the ground for delivering an instruction signal and to reduceprovisionally the hydraulic brake pressure upon reception of thedelivered signal so far as its delivery continues, so as to recover theexcessively retarded wheel speed to such a degree that the so adjustedwheel speed keeps pace with the occasional absolute speed of the vehicleso as to prevent possible wheel lock, and then to increase the brakepressure again, and so on.

Such repeated brake pressure releases and reapplications are thepredominant feature of operation of the antiskid hydraulic brakepressure control apparatus, or briefly antiskid apparatus" adapted forpreventing lateral vehicle skids.

Upon a brake pressure release or reduction during the cyclic brakingoperation, the rotational speed of the vehicle wheels will recover againnearly to the absolute running speed of the vehicle. This speed recoveryis introduced by the driving force which is transmitted from the groundsurface to the vehicle wheels. The amount of this counter drive forcedepends naturally upon the surface conditions of the ground. For smallervalue of the coefficient of adhesion appearing between the groundsurface and the wheel tires, the counter drive force will becorrespondingly smaller, and vice versa.

When the rear wheels are subjected to locking during the progress ofbrake application with the clutch mechanism coupled, so that thesewheels are making slips, the vehicles drive engine will be caused tostop. Even when the antiskid apparatus is brought into actuation at thisstage so as to reduce the hydraulic brake pressure to befed to the rearwheels, thus the brake application on to these wheels becoming weaker,the counter drive force of the above kind must cover at least the powernecessary for initiating engine restarting, added with variousmechanical losses in the transmission system of the vehicle. For smallervalues of coefficient of adhesion which means that the ground surfaceconditions are disad-. vantageous, the counter drive force mayfrequently be smaller than the necessary drive force of the above kind.In this case, the vehicle rear wheels may fail to reinitiate rotation,even when the antiskid apparatus is brought into function for releasingor reducing the hydraulic brake pressure fed to the rear wheels, whichmeans an unsatisfactory operation of the apparatus.

In order to avoid such unsatisfactory function of the antiskid brakingsystem, it is necessary to disengage the vehicle clutch in advance, toallow the antiskid apparatus to operate with trouble-free actionv Itshould be concluded therefore that a more effective skid prevention willbe realized by disengaging the vehicle clutch upon actuation of theantiskid apparatus.

It is therefore the main object of the invention to provide an improvedtechnique for allowing the antiskid apparatus to operate in a moreefficient way without inviting the aforementioned conventionaldrawbacks.

For the realization of the above object, the method accord ing to thisinvention resides in its broadest coverage the combination of thefollowing steps:

1. sensing a wheel lock during braking stage for vehicle wheels;

2. reducing the hydraulic brake pressure upon reception of aninstruction signal informing of a sensed wheel lock, and

3. interrupting at the same time the conventional clutch 5 meansinserted between the vehicle drive engine and the vehicle wheels uponthe reception of said instruction signal.

The apparatus for carrying out the above method resides in its broadestaspect in the combination of the following several constituents:

1. sensor for sensing an impending or realized wheel lock in the courseof a wheel brake application;

2. controller for receiving an instruction signal from said sensor andfor controlling hydraullic brake pressure being delivered to hydraulicwheel brake means in its pressurereducing direction upon reception ofsaid instruction signal; and

3. a releaser operatively connected with said controller for 20releasing the clutch upon actuation of said controller.

These and further objects, features and advantages of the invention willbecome more apparent as the description by reference to the accompanyingdrawings, in which:

FIG. 1 is a schematic general arrangement view of an ap paratus adaptedfor carrying out the method according to this invention.

FIG. 2 is an enlarged and longitudinal sectional view of a clutchbooster and its several related parts employed in the arrangement shownin FIG. 1.

In the following, a preferred embodiment of the invention will bedescribed in detail by reference to FIGS. 1 and 2.

In the drawings, the numeral represents a sensor operatively connectedwith vehicle wheels, not shown, for sensing the rotational conditionsthereof, the sensor being shown only in a highly simplified way by ablock by virtue of the very popularity of the design and function. 11denotes a switching means responsive to a skid sensor of the knownconstruction adapted for sensing an impending or already brought-aboutwheel lock which appears upon a sudden and considerable or excessapplication of brake pressure to the wheels. When a wheel lock should beencountered during brake application, a slip of vehicle wheel or wheelson the ground may he certainly invited which means, as commonly known, adangerous steering condition of the vehicle. Such a switching means asat 11 is highly known in its design and function among those skilled inthe art. The switching means 11 comprises a switch 12 which iselectrically connected, on the one hand, with a solenoid coil 13a ofair-vacuum changeover valve assembly generally denoted 13, and groundedthrough a current source 100, on the other hand.

The numeral 14 denotes antiskid control of known design which isfluidically connected through piping means 101 with said changeovervalve assembly 13. 5 A conventional manual brake actuator shapedpreferably into a foot-operated pedal 15 is operatively connected, asconventionally, with a master cylinder 16 of known construction, thelatter being connected hydraulically and directly through pipings 103and 104 to front wheel hydraulic brake means 17. Master cylinder 16 isalso hydraulically connected through piping 103, a part 14a of saidcontrol 14 and a further piping 105 to rear wheel hydraulic brake means18.

When the brake pedal 15 is actuated, pressurized oil will be directlysupplied from the master cylinder 16 to the front wheel brake means 17,but the braking conditions of the rear wheel brake means 18 is somewhatdifferent from that of the front wheel when a sudden and considerablebraking effort is applied to the pedal 15 in such a degree that a wheelslippage against the ground surface is invited during the brakeapplication. In this case, the sensor 10 is brought into actuation uponsensing such wheel slippage or lock, and switch 12 is turned to on,whereby the solenoid 13a of valve assembly 13 is energized and thepneumatic conditions in the control 14 are con ditioned, asconventionally, so as to perform the desired controlling function. Underthese operating conditions, pressure oil delivery to rear wheel brakemeans 18 is controlled in the brake efl'ort reducing direction forminimizing or obviating the rear wheel slippage, as is commonly known.The function of the control 14 will be described more in detailshereinafter.

The numeral 19 denotes an electromagnetic relay which is connectedelectrically in parallel to said switch 12 and provided with aself-maintaining coil 20. When the relay 19 is actuated, thereby itsmovable contact 21 being brought into engagement with its matingstationary contact 22 and self-maintaining coil being energized, the nowestablished engaging conditions between contacts 21-22 is preservedunder the magnetic influence of the maintaining coil, even upon anopening of said switch 12. This self-maintaining operation requiresnaturally the following preparatory design conditions. Morespecifically, a movable contact 23 is operatively connected with aswitch means 24 arranged to be on-off controlled by brake pedal 15 insuch a way that with the pedal kept in its actuated position switch 23is being closed. In this actuated conditions, a circuit comprising lead25; movable contact 21; stationary contact 22; coil 20; switch 23, andthe solenoid coil 26a of vacuum-air changeover valve assembly 26 ofclutch control, and further including the ground connection, is beingenergized even upon opening of the switch 12.

The valve assembly 26 is pneumatically and directly connected through apiping 28 with the right-hand chamber 106 of clutch booster 27, on theone hand, and connected pneumatically and indirectly through a piping 60and a control valve assembly 30 with the left-hand chamber 107 of thesame clutch booster, as clearly shown.

These chambers 106 and 107 are separated from each other by a diaphragmpiston 31 which is resiliently urged to move rightwards in FIG. 2 underthe action of a spring 32. As will be more fully described hereinafter,when said both chambers 106 and 107 are filled with a negative or vacuumpressure, the diaphragm piston 31 will be kept in its position shown.

A valve 33 is fixedly attached to a plunger 36 which is mounted slidablyin the horizontal or axial direction in the valve assembly26, said valvebeing arranged selectively to cooperate with either of valve seats 34and 35. The left-hand part of axial bore 109 provided in the housing 108of valve assembly 26 is kept in communication through filter material 37with atmospheric air, as shown.

The detail construction of clutch booster 27 and its attached controlvalve assembly 30 is shown in FIG. 2.

Clutch booster 27 comprises a housing 110 containing slidably saiddiaphragm piston 31, a plunger 38 being fixedly attached with its oneend to said piston at its center. The booster 27 comprises further abody member 39 which is rigidly connected with said housing 110,although the fixing means have been omitted from the drawing only forsimplification. The body 39 is formed with an axial bore 390 whichreceives slidably said plunger 38 having at its left-hand end asubstantially truncated cone-shaped projection 38a. In the axial bore39a there is a hollow and slidable piston member 40 having at itsright-hand end a correspondingly truncated coneshaped recess 40aarranged in opposition to said plungers projection 38a. The axial bore39a is closed at its left-hand end against which one end of spring 41abuts, while the opposite end of the latter is kept in pressure abutmentagainst the left-hand end of said hollow piston 40. An elongated stopmeans 42 is fixedly attached to the closed end of said axial bore 390and extends from the bore-closing end wall a considerable distanceconcentrically with the piston 40 and bore 39a, the right-hand end ofsaid stop means 42 invading into the piston bore 40b and constituting anenlarged end 42a acting as the stop per se. As will be easily supposed,the purpose of this stop means 42-42a is to limit the maximum allowablelength of expansion of said pring 41.

In the position shown, there is a gap distance between the plungersprojection 38a and the recessed piston end 40a, so as to establish anintermediate space 39b which is kept in fluid communication through alateral port 44 with clutch master cylinder assembly 43. In closeproximity of the closed end of the bore 390, there is provided a furtherlateral bore 46 which is fluidically connected with a clutch-releasecylinder assembly 45.

Control valve assembly 30 is fixedly attached to the body member 39, theinterior space of said valve assembly being divided into two separatechambers 57 and 58 by means of a diaphragm piston 47 which is connectedmechanically through connecting means 111 with a plunger 48 slidablyreceived in a recess 112 formed in the body member 39 and kept in fluidcommunication with a duct 49 through a ring space 39c formed in thematerial of the body member 39, if the plunger 48 should be neglected,said duct 49 communicating fluidically with said intermediate chamber3%.

Even when the booster 27 is actuated, the plunger 38 is brought intoengagement with the piston 40, thus the effective volume of saidintermediate chamber becoming nil, port 44 is still kept in fluidcommunication with duct 49 through the intermediary of the ring space390.

Valve elements 50 and 51 are rigidly connected together by means of aconnecting rod 113. A compression spring 52 is inserted between valvemember 50 and a separation wall 114 made integral with the housing 30a,whereby the other valve element 50 is urged to move towards its valveseat 53 formed in the separating wall 114. Valve element 51 is arrangedso that it can cooperate with valve seat 54 formed in the diaphragm 47at its center.

When the plunger 48 is moved downwards from its position shown, thevalve seat 54 of diaphragm 47 is brought into pressure engagement withthe valve element 51, thereby the hitherto established fluidcommunication between chambers 57 and 58 being interrupted.

With further downward movement of plunger 48, the valve element 50 isseparated from its cooperating valve seat 53, thereby the ambientatmospheric air being brought into communication through air filter 55with the chamber 58. Communication passage 59 bored through the bodymember 39 serves for establishing fluid communication between the saidchamber 57 and the left-hand chamber 107 of booster 27.

Control valve assembly 30 is further formed with a port 60 which servesfor establishing fluid communication of the chamber 58 with theright-hand chamber 106 of booster assembly 27 through the valve assembly26.

Numeral 61 denotes a conventional clutch-releasing lever and numeral 62represents a conventional clutch pedal.

As will become more apparent from the following disclosure of operationof the present apparatus, when the brake pedal is kept in its actuatedposition and a wheel slip is sensed, the clutch can be released withoutactuation of the clutch pedal, thereby increasing considerably thedesired antiskid effeet.

When the brake pedal is actuated so as to apply brake, pressurized oilis fed directly from the master cylinder 16 to front wheel brake 17,while pressurized oil will be conveyed from the master cylinder 16through the control 14 to rear wheel brake 18.

When there is no slip appearing between vehicle wheels and the groundsurface, same oil pressure will be conveyed to the front wheel brakemeans as well as to the rear wheel brake means. If there is sensed awheel slip, sensor 10 is actuated and electric instruction signal willbe conveyed to switching means 11, thereby switch 12 is brought into itsclosed position, thus, as commonly known, changeover valve assembly 13being thereby actuated and the control 14 is also brought intoactuation. In this manner, pressurized oil delivery from the mastercylinder 16 to rear wheel brake 18 is interrupted, and at the same timethe oil pressure being delivered to rear wheel brake is reduced, so asto prevent further wheel slippage. At the same time with closure saidswitch 12, relay 19 is brought into actuation, movable contact 21 isbrought into engagement with stationary contact 22. It should be notedthat since switch 24 actuated by brake pedal 15 is turned to on" uponactuation of brake pedal 15, switch contact 23 is also in itson-position. In this way, the solenoid of changeover valve assembly 26is energized, so as to move the valve 33 rightwards from its positionshown until it engages with valve seat 34, thereby the fluidcommunication between passages 28 and 60 being interrupted. By therightward movement of the valve 33, the opposite side thereof is broughtinto separation from valve seat 37, thereby passage 28 brought intofluid communication through air filter with the ambient atmosphere.Thus, diaphragm 31 of booster 27 will move leftwards from the positionshown. By the actuation of changeover valve assembly 26 in theabove-mentioned manner, only the right-hand chamber of diaphragm 31 isbrought into communication with the atmospheric air, thus the diaphragmbeing pneumatically caused to move in the left-hand direction. With thisleftward movement of the diaphragm, plunger 38 is also moved leftwardscorrespondingly and its end projection 38a being brought into tightengagement with the correspondingly recessed piston end 40a. Withfurther leftward movement of the plunger, the oil pressure prevailing inthe left-hand chamber of piston 40 is increased and conveyed to clutchreleasing cylinder 45, thereby clutch-release lever 61 being actuated soas to release the clutch. 4

It will be seen that upon actuation of the skid-sensing means, theabove-mentioned operation will be brought about and the clutch will bereleased without any intentional actuation of clutch pedal by thevehicle driver.

By the provision of switch means 24, self-maintaining coil and switchmeans 23 and in spite of occasionally invited intermittent action of theantiskid control apparatus, thus intermittent on off action of switch 12being invited, the solenoid of air-vacuum changeover valve assembly 26does not follow after the above-mentioned intermittent on-off operation.In this way, the clutch is disengaged so far as the brake pedal is beingactuated.

In case of the antiskid control apparatus failed to operate, or in caseof the whole arrangement acting in the regular manner, actuation ofclutch pedal 62 causes the pressurized oil from clutch master cylinder43 to be conveyed at first to the intermediate space between the innerend of plunger 38 and the corresponding end of piston 40, thence throughport or passage 49 to the cylinder for piston 48 of control valveassembly 48. In this way, diaphragm 47 is urged to move outwardly andits valveiseat 54 is brought into pressure engagement with valve element51, thereby the fluid communication between ports 59 and 60 beinginterrupted. At the same time, valve element 50 is caused to separatefrom its mating valve seat 53 and passage 60 is brought intocommunication with the atmospheric air. The pneumatic action is conveyedthrough changeover valve assembly 26, which has been brought into itsposition shown in FIG. ll, upon diaphragm 31, the latter being caused tomove leftwards in FIG. 2 for releasing the clutch. Even with the plunger38 brought into engagement with piston 40, passages Ml and 49 being keptin fluid communication through ring space 39c, diaphragm 47 is returnedto its shown position under the influence of return spring 64, byintentional release of the clutch pedal by the vehicle driver, thus theclutch being also returned to its original position.

There is provided a port 65 at the outer end of the piston 40. This port65 serves for allowing a trouble-free return movement of piston 40 underthe action of return spring 41.

As will be noted from the foregoing disclosure, the invention provides aunique combination of the clutch booster with the antiskid controlassembly, thereby providing an automatic clutch release and thus anautomatic release of the functional combination between the vehicledrive engine and the vehicle wheels, should there a wheel slip besensed, and, indeed, without intentional actuation of the clutch pedalby the vehicle driver. By this measures, therefore, the necessary energyfor the restarting of the engine at this stage can be saved. As aresult, the overall engine drive costs can be saved considerably and atthe same time the desirous prevention of wheel slippage caused by theapplication of excess braking effort can be realized in a highlyeconomical and effective manner.

What we claim is:

1. An apparatus for the simultaneous control of antiskid brake means andclutch means comprising, sensor means for sensing substantial wheel lockconditions in the course of brake application and for delivering aninstruction signal, control means for controlling hydraulic wheel braltepressure being delivered from a master cylinder to said brake means,said control means being operativelly connected with said brake meansand said sensor means to reduce said pressure upon reception of saidsignal to release said brake means and to increase said pressure whensaid signal ceases to reapply said brake means, and release meansoperatively connected with said clutch means and said sensor means forautomatically releasing said clutch means upon initial reception of saidsignal and maintaining said clutch means released during subsequentrelease and reapplication of said brake means by said control meansduring a single continuous braking operation.

2. An apparatus as set forth in claim 1 wherein said release meansincludes hydraulically operated clutch-releasing' means, clutch boostermeans operatively connected to said clutch-releasing means and havingtwo chambers separated by a movable piston for boosting hydraulicpressure in said clutch-releasing means, and changeover valve meansoperatively connected with said clutch booster means and said sensormeans and responsive to said signal for controlling said clutch boostermeans.

3. An apparatus as set forth in claim 2 wherein said release meansfurther comprises first passage means connected between said twochambers, said changeover valve means being provided within said firstpassage, second passage means connecting a clutch master cylinder with aclutch-releasing cylinder, third passage means normally connecting oneof said chambers with a vacuum source, slidable means adapted tocooperate with said piston for on-off control of said second passagemeans, and spring means for urging said piston in its opening directionof said second passage means whereby upon reception of said signaloperating said changeover valve means, the pressure differential in saidchambers will be controlled so as to move said piston in a direction inwhich said passage means is interrupted.

ll. An apparatus as set forth in claim 3 wherein a control valve meansis disposed between said. clutch booster means and said changeover valvemeans, said control valve means comprising two chambers separated by adiaphragm piston, one of said chambers being connected with one of saidchambers of said clutch booster means and the other of said chambersbeing connected with said changeover valve means, said control valvemeans further comprising valve means responsive to foot pressure exertedupon a clutch pedal and including a first valve element for on-offcontrol of passage means connected between said chambers of said controlvalve means and a second valve element for on-off control of passagemeans connected between the other of said chambers of said control valvemeans and the atmosphere.

5. An apparatus as set forth in claim 2 further comprising circuit meansadapted to electrically connect said sensor means with said changeovervalve means and for electrically connecting said sensor means with saidcontrol means, said circuit means comprising switch means operable bysaid sensor means, relay means electrically connected with said switchmeans and provided with holding means, additional switch means operableby said relay means and brake pedal operated switch means.

6. A method for hydraulic brake and clutch control com prising sensing asubstantial wheel lock condition during braking of a vehicle, providinga signal in response to said sensing to automatically control means forreducing and increasing hydraulic brake pressure, simultaneously andautomatically releasing the clutch means of the vehicle upon the initialreception of said signal.

1. An apparatus for the simultaneous control of antiskid brake means andclutch means comprising, sensor means for sensing substantial wheel lockconditions in the course of brake application and for delivering aninstruction signal, control means for controlling hydraulic wheel brakepressure being delivered from a master cylinder to said brake means,said control means being operatively connected with said brake means andsaid sensor means to reduce said pressure upon reception of said signalto release said brake means and to increase said pressure when saidsignal ceases to reapply said brake means, and release means operativelyconnected with said clutch means and said sensor means for automaticallyreleasing said clutch means upon initial reception of said signal andmaintaining said clutch means released during subsequent release andreapplication of said brake means by said control means during a singlecontinuous braking operation.
 2. An apparatus as set forth in claim 1wherein said release means includes hydraulically operatedclutch-releasing means, clutch booster means operatively connected tosaid clutch-releasing means and having two chambers separated by amovable piston for boosting hydraulic pressure in said clutch-releasingmeans, and changeover valve means operatively connected with said clutchbooster means and said sensor means and responsive to said signal forcontrolling said clutch booster means.
 3. An apparatus as set forth inclaim 2 wherein said release means further comprises first passage meansconnected between said two chambers, said changeover valve means beingprovided within said first passage, second passage means connecting aclutch master cylinder with a clutch-releasing cylinder, third passagemeans normally connecting one of said chambers with a vacuum source,slidable means adapted to cooperate with said piston for on-off controlof said second passage means, and spring means for urginG said piston inits opening direction of said second passage means whereby uponreception of said signal operating said changeover valve means, thepressure differential in said chambers will be controlled so as to movesaid piston in a direction in which said passage means is interrupted.4. An apparatus as set forth in claim 3 wherein a control valve means isdisposed between said clutch booster means and said changeover valvemeans, said control valve means comprising two chambers separated by adiaphragm piston, one of said chambers being connected with one of saidchambers of said clutch booster means and the other of said chambersbeing connected with said changeover valve means, said control valvemeans further comprising valve means responsive to foot pressure exertedupon a clutch pedal and including a first valve element for on-offcontrol of passage means connected between said chambers of said controlvalve means and a second valve element for on-off control of passagemeans connected between the other of said chambers of said control valvemeans and the atmosphere.
 5. An apparatus as set forth in claim 2further comprising circuit means adapted to electrically connect saidsensor means with said changeover valve means and for electricallyconnecting said sensor means with said control means, said circuit meanscomprising switch means operable by said sensor means, relay meanselectrically connected with said switch means and provided with holdingmeans, additional switch means operable by said relay means and brakepedal operated switch means.
 6. A method for hydraulic brake and clutchcontrol comprising sensing a substantial wheel lock condition duringbraking of a vehicle, providing a signal in response to said sensing toautomatically control means for reducing and increasing hydraulic brakepressure, simultaneously and automatically releasing the clutch means ofthe vehicle upon the initial reception of said signal.